But even if something's in the contract, it might well still be 'conveniently' forgotten about if it's to the employer's disadvantage. It's then that one has to remind one's employer of what the contract has stipulated in order not to be cheated.

What you describe above has happened to me on more than one occasion here in China. I spoke up about it in a polite way on each occasion. After doing so, I was not cheated at all. But I became persona non grata in the university's eyes. You see, the Chinese are not good at disguising their true feelings. When they try to pretend, their body language betrays them. Chinese university teaching staffs often have an entitlement mentality, and expect foreigners to be forever grateful for having been given teaching positions at their venerable seats of learning! I suspect that unlike me my foreign colleagues were in fact cheated, because they did not mention it so as to keep on the right side of the university. But if one points out a breach of contract to a Chinese employer, it's true that one isn't doing oneself any favors re the possibility of a contract extension. Personally, I didn't care about that. I've never worked anywhere in China where things were markedly better than anywhere else, so I never had any regrets about moving on after having spoiled my chances of being retained resulting from insisting on the terms and conditions of my contract to be met. Actually, my experience of Chinese tertiary education is that it's substandard and no university is significantly better than any other as a place to work at. I'm not saying the top few aren't like that, I just don't know. But my qualifications aren't top notch, so I couldn't get a job at that kind of university anyway.
While on the subject of university education in China, I should mention a podcast that I found very interesting. The details of it are below: I hope you enjoy listening to it, as I have done. It seems that Chinese universities are not alone in the world in being ropey, and that plagiarization at one of the better ones in America was a big problem! That was in 2003, but even so I wouldn't expect that things will have changed much there in the meantime!

CLASSIC LNL: The Twilight of American Culture

http://www.abc.net.au/rn/latenightlive/stories/2011/3258596.htm